still can't plant a tree - what am i doing wrong?

Nine times out of ten it's depth. The root flare - where the trunk widens out at the bottom - should sit at ground level or a touch above, not buried. Dig the hole two or three times as wide as the root ball but no deeper, tease out any roots circling the pot, and backfill with the soil you took out rather than pure compost, or the roots never leave the nice soft pocket. Water deeply, then mulch in a ring that doesn't touch the bark. What's actually happening with yours - dying after planting, or just sitting there not growing?